The present disclosure generally relates to enhancing images from electronic displays, and specifically to generate aberration corrected images based in part on a measured accommodation of a user's eye.
A head mounted display (HMD) can be used to simulate virtual environments. Such an HMD includes optics which may introduce aberrations into images presented to the user. Conventional HMDs are often unable to fully compensate for aberrations introduced by the headset optics when rendering content. Moreover, being able to reasonably determine where the eyes of a user accommodated is required for accurately rendering blur as a depth cue in virtual reality (VR) and augmented reality (AR) displays. Knowledge of the accommodative state of the eye is also valuable for varifocal HMDs, as well as multi-planar and volumetric displays.
Vergence and accommodation are neurally linked. In current variable-focus HMDs, the accommodation state of the eye is inferred by tracking the eyes vergence state and trying to estimate the position in depth of the user's eye gaze. This indirect estimation of the accommodative state of the eye is good enough for some applications; however, because of individual variation in prescriptions, and accommodation dynamics, this is a sub-optimal solution. For example, this requires using a derived average of response time across the population for the accommodation response, which may result in an incorrect positioning of the focal plane dynamically, incorrect blur and depth cues, and artifacts in the displays perceived quality, perceived contrast and quality.
Other multi-focal based volumetric methods for presenting stimuli provide a more natural cue to accommodation; however, these methods suffer from engineering and visual challenges. First, because the eye is receiving the sum of light energy from spatially aligned pixels, the alignment of image planes in front of the eye is critical. Secondly, because the eye is usually defocused to the image planes when viewing content, this formulation of a light-field display suffers from reduced contrast and reduced image quality. This can be rectified by adding a variable focus element to the volumetric display. However, this comes with added engineering challenges, and has yet to be proven.
Moreover, vergence-based estimates of accommodation state have yet to prove accurate enough to position an image plane for optimal sharpness.